Emotet — Office (OOXML) / .XLSX malware analysis

Static analysis result for SHA-256 d7416375deea2edd…

MALICIOUS

Office (OOXML) / .XLSX

1.16 MB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300 First seen: 2022-04-20
MD5: 2cce1f8d9c75ad39b12704d57f666af1 SHA-1: cbecb1d7fcfbf2f0ce33a2f043dc85d6e764181a SHA-256: d7416375deea2edd724d9429d0d3b26f4a120aaa66fb51fecf47f1fb6567fdb0
200 Risk Score

Malware Insights

Emotet · confidence 95%

MITRE ATT&CK
T1059.005 Visual Basic T1105 Ingress Tool Transfer T1059.001 PowerShell

The critical heuristic 'OOXML_XLM_BINARY_WINAPI_STRINGS' indicates the presence of Excel 4.0 macros that utilize WinAPI functions and download strings. The extracted script confirms this, showing the use of 'Kernel32.CreateDirectoryA' to create a directory 'C:\Jhfrg'. It then proceeds to save multiple files (e.g., 'C:\Jhfrg\Rgsrhda.ooocxx') using 'regsvr32' which is commonly used to download and execute payloads. The ClamAV detection further supports the Emotet family attribution.

Heuristics 4

  • Excel 4.0 macro sheet (1 sheet(s)) critical OOXML_XLM_MACROSHEET
    Spreadsheet contains an Excel 4.0 (XLM) macro sheet — XLM was a major Office malware vector during 2020-2022 and evaded many VBA-focused controls before Microsoft tightened XLM defaults. Even legitimate XLM use is rare in modern workbooks. The macro sheet is stored as XLSB/BIFF12 binary content, which many XML-only OOXML scanners miss.
  • Binary XLM macro sheet with WinAPI/download strings critical OOXML_XLM_BINARY_WINAPI_STRINGS
    Excel 4.0 macro sheet is stored as BIFF12/XLSB binary data and contains Win32 download or process-execution API strings such as URLDownloadToFileA, ShellExecuteA, or CreateDirectoryA. These strings are high-signal in XLM macro sheets and catch payload-download macros that XML-formula scanners cannot parse.
  • ClamAV: Xls.Downloader.Emotet-OOXML_XL-af43432fbcb8603c-9980048-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Xls.Downloader.Emotet-OOXML_XL-af43432fbcb8603c-9980048-0
  • Embedded OLE object medium OOXML_OLE_OBJECT
    Document contains an embedded OLE object

Extracted artifacts 4

Files carved from inside the sample during analysis.

FilenameKindSourceSize
ooxml_oleobject_00.bin
91be447cf4ed5b5fa18315c6180ef6d62647686972b570319f960439fe37d717		 ooxml-ole-object OOXML embedded OLE part: xl/embeddings/oleObject3.bin 3099136 bytes
ooxml_oleobject_00_ole10native_00.bin
a6724425b761391a2288cdb0e402bdc8cf2de9a4e93260c95af92b78344a367e		 ole-package OOXML xl/embeddings/oleObject3.bin Ole10Native stream: Ole10Native 3072068 bytes
emf_00.emf
3f0f6bb70f3d65dcc8d248d78ac320bcc22b1148ea5fdd2c1043065d03460133		 ooxml-emf OOXML EMF part: xl/media/image1.emf 6144552 bytes
xlm_sheet_00.bin
69a2e1d9485c0dfa0a658594ddc6d39e897b39125ece8f4c2b2985736ffbc1c7		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.bin 2137 bytes

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